Crude oil containing paraffin creates pumping and flow problems in that paraffin deposits build up within the well tube and upon the pumping apparatus, such as the sucker rod, at the upper regions of the well tube and rod as the majority of paraffin deposits occur within one thousand feet of the well head.
The paraffin build up problem is severe enough to interfere with the flow of oil from the well tube and in extreme cases, to prevent oil flow all together. Further, as the paraffin deposits increase, the frictional forces upon the sucker rod become greater and higher energy requirements for pumping occur. In the past, paraffin deposits have been controlled by the use of scrapers mounted upon the sucker rod, and by otherwise physically removing the paraffin from the well tube. Also, it is common to flush the well tube with a hot fluid, such as heated oil or water, and the injection of such heated fluid into the well tube at the well head will melt the paraffin and force it into the oil bearing formation. While such oil treatments temporarily clear the well tube and the associated well components of paraffin, eventually, the paraffin again enters the well tube, the deposits reoccur, and also, the oil flow characteristics of the oil bearing formation can be adversely affected by forcing the melted paraffin into the formation.
A variety of methods and apparatus have been proposed for controlling paraffin deposits within oil wells, and such proposals are typified in the disclosure of U.S. Pat. Nos. 2,293,442; 2,300,348; 2,704,979; 3,014,531; 3,542,130; 4,011,906 and 4,049,057. However, methods and apparatus such as shown in the aforementioned patents each have shortcomings which prevent such disclosures to be considered the solution to the paraffin problem, and it is still common practice to periodically deparaffin oil wells by unseating the bottom hole pump, introducing heated oil into the well tube to melt the paraffin deposits and forcing the oil containing the melted paraffin into the oil bearing field, resulting in high cost, extensive pumping down time, and contamination of the oil bearing formation.
It is an object of the invention to provide a method of removing paraffin from an oil well wherein well pumping is not interrupted, and the oil bearing formation is not contaminated.
Another object of the invention is to provide a method for removing paraffin from an oil well utilizing hot fluids wherein heating of the paraffin deposits occurs both from indirect and direct contact with the heated fluid.
An additional object of the invention is to provide a hot oil system for paraffin control in oil wells wherein heated fluid is conveyed to the well tubing at a location below the paraffin forming depth and the fluid containing the melted paraffin is removed from the well at the well head.
Yet another object of the invention is to provide apparatus for removing paraffin from oil wells wherein the apparatus includes a hot oil conduit concentrically related to the well tubing and the conduit communicates with the well tubing below the paraffin forming depth.
A further object of the invention is to provide a hot oil paraffin removing system for oil wells utilizing a hot oil conduit concentrically related to the well tubing, and wherein a check valve is located within the hot oil conduit preventing pumped oil from entering the conduit.
In the practice of the invention a hot oil conduit is located within the well substantially concentric to the well tubing through which oil is removed. The conduit extends to a depth usually slightly below the paraffin forming well depth, and the conduit lower end is sealed with respect to the well inner tube. The concentric conduit has an inlet at the well head and ports defined in the well tube establish communication between the well tube and hot fluid conduit adjacent the conduit lower end. A check valve located within the conduit prevents pumped oil from entering the conduit to a significant extent, and during normal well pumping operations, the flow of oil is through the well tubing and well head, in the usual manner.
When it is desired to remove paraffin deposits, a hot fluid, usually hot oil, is heated and introduced into the conduit at the well head. As the heated oil moves downwardly through the conduit, it will heat the walls of the well tube melting paraffin deposits within the tube, and as the hot oil flows through the check valve and into the inner tube and through the ports due to the fact that the pressure within the conduit is greater than that within the tube, the hot oil will rise within the well tube heating the oil therein, and have direct contact with paraffin deposits within the well tube, and the hot oil and melted paraffin is removed from the well head. Depressurizing the hot oil conduit permits the check valve to seat whenever the pressure within the well tube exceeds a predetermined limit as when pumping.
The check valve is of an annular form inexpensive to manufacture, and the apparatus associated therewith permits trouble free service over long periods of time.
The practice of the invention saves approximately two thirds of the conventional cost of deparaffining a well, saves substantial time, and results in an improved "cleaning" of the well tubing, and depositing of the paraffin within the oil bearing formation is eliminated. The ability to "hot oil" an oil well while the well is still pumping and producing is of great advantage with respect to minimizing loss of revenue, and the apparatus and concepts of the invention are of such nature as to be readily understood and implemented by relatively low skilled operators.